Stay-bolt tap



G. M. BRUBAKILR, JR.

STAY BOLT TAP. APPUCMION FILED JAN. B. 1920.

Patented Nov. 7, 1922.

Patented Nov. 7, 1922.

UNITED STATES PATENT OFFICE.

GORDON M. BRUBAKER, JR., OF MILLERSBUBG, PENNSYLVANIA, ASSIGNOR TO W. L.

' BRUBAKER & BROS. COMPANY, OF MILLERSBURG. PENNSYLVANIA, A CORPORA- TION.

STAY-BOLT TAP.

Application filed January 8, 1920. Serial No. 3550.074.

To all whom it may concern:

Be it known that l. Gonnox Mann 13m;- BAKER, Jr.. a citizen of the United States. residing at Millershurg. in the county ot Dauphin and State of Pennsylvania. have invented new and useful Improvements in Stay-Bolt Taps. of which the following is a specification.

My invention relates to stayholt taps. and its objectis to providea stayholttap with spiral flutes or 'rooves so arran ed and coo ierating with the reaming rutting edges and tapered and straight threml-rutting and thread-finishing portions of the tapered shank of the tool as to secure certain novel and eflicient actions and desirable advantages, to \vit, -lirst, to make the tap cut easier in order to give it more revolutions per minute. thus reducing the time required to tap holes: second. to throw the ehi out of the hole and lessen the chance of corrilph ing the threads: third, to enable ac urate holes to be tapped in less time and with less wear and tear on the threads than with taps of ordinary construction: and. Fourth. to reduce the jerking ol the tap which is so often the cause ol the threads breaking.

I attain these objects by the construction shown in the aecom mnying dra\\ing. in which the ligurc shown i:-: a view in side elevation of' a staybolt tap embodying my invention.

Referring to the d rawing. l designates the shank of the tool which comprises the Forward roamer portion 2, the intermediate tap portion 3, and the rear tang portion 4. said tang portion having the usual angularend 5 by means of which it may be turned. .\s

shown, the tap portion 3 has two threaded surfaces, to wit, a forward thread cutting surface extending between the points 1' and 7 and composed of tapered threads 8. and a rear thread finishing surface extending between the points 7 and f) and composed of uniform threads 1.) said threaded surfaces intersecting at the point 7. Also as shown. the reamer portion 2 extends from the extreme forward end of the tool. which in the drawing is broken away. to the point 6. The reamer porton and threaded surfa es of the tap portion are thus Withoutseparation or break. or. in other words. are continuous with each other.

The shank is formed with longitudinal flutes or grooves 11 producing the spiral ribs 12 on which the threads 8 and, 10 are formed. The edges 13 of these ribs also form the reaming cutters. As shown, the grooves 11 extend the full distance from the lorward end of the shank to the point of intersection 9 between the working portion of the shank and the tang 4, the grooves thus providing clearance channels for the redeption and discharge of the chips from both the reaming and the thread cutters. The essence of my invention consists in extending these grooves spirally, instead of making them straight and parallel, as in stayholt taps of ordinary construction. By this means I obtain the following advantages: First, the reaming edges 13, being arranged to cut on a spiral line, not only facilitate the cut,but cut with greaterease and smoothness. Flll'tl'lQl'l'IlUlB, by extending them at an angle to the axis of the shank, the cutting edges are arranged for a shearcutting action and are more firmly hacked by thc ribs in the direction of the line of cut, and hence the cut may be made with reater rapidity and with less liability of tie cut ting edges forming fins or ragged cuts and causing undue friction :.id heating, or of the cutting edges b nding or hanging and causing the shank to snap. a l ault common with ordinary stayholt taps having straight parallel grooves. Secondly. the spiral flutes and rihs dispose the threads 8 and [0 at an angle. with similar advantages in more t'recly and easily cutting and finishing the threads and discharging the shavings into the clearance grooves. At the same time the threads 8, by being arranged at an angle, not only begin the work of forming the threads but also divide up the coarser chips formed by the reaming cutters, thus allowing the threads to cut with less resistance and liability of injury and to (lo smoother and hetter work. This also avoids the necessity of cross-grooving the ribs of the reaming portion in order to divide the chips formed hy the cutting edges thereof. so that it is not necessary to weaken the tool at the point, mentioned Where it is subject to great strain. 'l 'hirdly the spiral formation of the grooves and ribs causes the chips to be separated and thrown into the grooves. thus reducing friction, wear and tear upon the cutting and threading vents the tool from canting and surfaces, and th tendency of the tool to choke and hang in the bore with disastrous results.

It will be observed that the' surfaces 2 and 8 extend on a continuous (continuously uniform) taper from the forward end of the ream'er to the point 7, where the tapered threads 8 intersect the uniform threads, and thatthe threads 8 begin directly at the point of termination of the reamer, while the first thread of surface 10 is a continuation of the secting at the point where the'tapered portion of the tool mergesinto the portion of uniform diameter on which threads 10 are formed. By this construction thetool has acontinuous chip-breakingaction throughout the lengths of the. reamin and tapping portions, also a continuous c earance action, and each working surface comes into action immediately upon the cessation of action of the receding surface, so that in the finished pro not it is impossible to tell where 'one acting surface has left off cutting and the succeeding acting surface be an cutting.

's avoids liability of the too? hanging in the bores and damaging the work, and reof line and cutting crookedly, and insures the production of perfectly finished work. Hence the tool is articularlyvaluable for use in reaming and tappingstaj bolt holes in two spaced boiler sheets at iii-time, as a perfect lead and centering action is obtained, insurin the boring 1'' true and absolutely alined oles without irregularity of action liable to cause vibration of a loose sheet or the tool, the cutting of irregularl shaped holes vlbration, or t e binding or eter of said tapered shank being provided with s the breakage of the tool due to irregular alinements or vibratory motions.

It will, therefore, be reagiiiily understood that I obtain the objects an advantages set forth in a simple and eificient manner and produce a tool which is more reliable, ra id and eiiicient in action and much less lia Is to break than staybolt taps of ordinary co struction, a very desirable advantage in view. of the general structural weaknesses of longto and slender tools of this character. aving thus fully described my inverttion, claim: if i s a new and improved article of facture, a stay bolt tap comprising a s having a forward tapered reaming po a rear tang portion, and an intermedi tap (portion, said tap portion having a forwar threading surface continuous. with said reaming portion and com osed oi 6Q tapered threads of succesively and progress-1.

siv ely increasing diameter constitutingTii.

uniform continuation of the taper oi the reaming portion and a rear threading $51 face composed of threads ofiiike diametercontinuous with and corresponding in diam e V eter to the final thread'of largestl diam threads, the said iral clearance y between thegrooves extending continuous tip of the reaming portion and the tan", said grooves producing spiral ribs havi shear-cut reaming edges and on which said tool. my signature.

at an angle to the axis of the In testimony whereo I aflix 

